Many of today's computing systems include computing resources that are not fully utilized. Such underutilization provides a potential opportunity to the owners of these systems to obtain greater capacity or cost reduction through improving utilization of these computing resources.
A number of approaches could be used to address the problem of improving utilization, including consolidation of multiple applications onto a single hardware platform. Consolidation approaches typically attempt to support the co-existence of multiple applications on a single unit of hardware in order to achieve greater function from fewer hardware platforms. A variety of computing resource management techniques could be used for this purpose.
Such computing resource management extensions, however, must address security and management issues arising from the concurrent execution of multiple applications on a single platform. For example, if web server applications belonging to two or more “untrusting” parties, i.e., market competitors, for example, are co-located on a single hardware platform, neither party will be content with the other party's having access to that party's private information. Some computer system functions, including for example, facilities to allocate and use hardware resources, i.e., network connections, DASD, output devices, and so forth, file system resources and communications resources could be used by one untrusting party to access the information or applications of another party if access is not controlled. Accordingly, in environments where users do not trust each other to perform system resource related tasks, the system administrator may be burdened with responsibility of performing each action involving critical system resources at significant time and expense.
One approach to the utilization and security issues arising in consolidation techniques is to partition machine resources among a number of logical partitions (LPARs) or virtual partitions (VPARs), effectively creating multiple machine images on a single platform. Such logical partitioning approaches potentially provide complete isolation among applications based in different machine images. A number of issues arise, however, with logical partitioning approaches. Such approaches may require implementation of hardware support (such as the introduction of an additional privilege level) to isolate privileged programs such as operating system kernels. Also, logical partitioning may require that the system administrator manage the configuration for the logical partitions and the allocation of resources among the logical partitions.
In another possible approach, one or more instances of operating system images that execute concurrently on a single hardware platform provide a plurality of “Virtual Machines.” In such approaches, each virtual machine may be a separate operating system instance that provides isolation for programs running in the virtual machine from other programs running in a second virtual machine. While such virtual machine approaches provide isolation between applications, other issues with such approaches may arise. For example, it may not be necessary, or even desirable to have multiple instances of an entire operating system for some applications. The complexity of administration and management for different operating systems images may weigh in favor of more simplified approaches.
Another approach would be to implement compartmentalization into a number of operating system functions. For example, some operating systems employing hierarchical file systems include a function to provide a level of compartmentalization by limiting file system access to a particular process. Such mechanisms, however, also suffer drawbacks. For example, a process's visibility of the file system name space may be limited to a single subtree of the file system in many implementations. Thus, compartmentalization typically does not extend to the process or networking spaces, making observation and interference by other processes possible.
A yet further approach would be to confine a process and its progeny (i.e., parent and children) to compartmentalized allocations of system resources, i.e., file system, network facilities, and so forth. In this approach, a process placed in such a compartment, termed a “Jail,” would have access to allocated system resources, but no visibility nor access to files, processes or network services outside of the Jail. A number of issues arise with the Jails approach, as well. Typically, Jails have no independent existence apart from the process for which the Jail is created. In other words, once the process creating the Jail (and its progeny, if any) terminates, the Jail terminates. Also, a second process cannot “join” a Jail.